largely dependent on remote sensing devices, still requires in field techniques to accurately determine the validity of the data. These tools and techniques range from simple, such as a depth spike, to complex, such as the core sampling machines used to check for variations in ice composition. Three common types of terrestrial measurements are: Snow Depth-This is a measurement from the snow surface to the ground in meters. It is commonly does over a large time span using immobile graduated stakes. Snow Water Equivalency- A measuring tool which represents the vertical depth of water that would accumulate in an area, if all the snow and ice were melted in that given area. Snow Density- This is the value found by dividing the water equivalency measurement by the snow depth reading. Remote Sensing Remote sensing technology is a recent tool in the field of snow hydrology that was developed in response to a growing outlook in the parametric studies (study of a subject over time) of hydrology formed in the mid 19th century. Compared to the deterministic (concept that there are no random events) approach used in earlier years, this technique created minimal human interaction with the environment and in field equipment. Currently there are thousands of sensing sites around the globe. Each site is capable of receiving data from any number of remote sensing techniques. The Landsat-MSS is one of the most common used tools. It is capable of detecting and categorizing snow cover into three zones for data calculations. The first zone is an area with 100% snow cover. The second zone is known as the transition zone, which is a mixture of snow covered regions and non snow covered regions. This zone is commonly measured at a 50% snow composition value. The Final zone is snow-free (=aper). The combined reading of these three measurements creates a relatively accurate estimate for the amount of snow within the scanned region. Several detrimental variables for this technique are cloud cover, extreme sunlight and heavy vegetation. Detection Tools As of 2004, every continent, with the exception of Antarctica has been under regular surveillance through the use of remote sensing satellites. Several sensing tools are listed below: Landsat multispectral scanner system (MSS) Thermatic Mapper (MT) Systéme Probatoire d’Observation de la Terre-multispectral (SPOT-XS) National Oceanic and Atmospheric Administration-Advanced Very-High Resolution Radiometer (NOAA/AVHRR) Marine Observation Satellite-Multispectral Electronic Self-Scanning Radiometer (MOS-MESSR) Indian Remote Sensing Satellite-linear imaging